Counterbalanced expansion roof



2 Sheets-Sheet l P. S. GRAVER Filed Feb. 7, 1944 COUNTERBALANCED EXPANSION ROOF Nov. 19, 1946.

INVENTOR. P/zzZLp. Graver;

ilLF I- aliiil llliii Patented Nov. 19, 1946 COUNTERBALANCED EXPANSION ROOF Philip S. Graver, Chicago, 111., assignor' to Graver Tank & Mfg. 00., Inc., East Chicago, Ind., a

corporation of Delaware Application February 7, 1944, Serial No. 521,334

7 Claims.

The invention relates to storage tanks having movable roofs and has reference more particularly to improved counter-balancing means for such movable roofs.

The Graver Patent 2,277,398 granted March 24, 1942, discloses a storage tank for volatile liquids having a roof capable of vertical movement to vary the vapor space within the tank. Since the roof of the storagetank, as shown in said patent, will operate at pressures higher than the maximum safety pressure for cone roofs of tan'ks con nected to it, it is desirable to reduce the operating pressure on said movable roof. Accordingly, an"

as a, result will be only one-half the weight that would be otherwise required.

A further and more specific object is'to'provi'de counter-balancing means for an expansion roof including an arrangement of double sheaves, cables and weights for reducin by half the required weight of the latter with a corresponding reduction in size of the cable and sheaves but whereinsaid weights'will move twice the distance travelled by the expansion roof.

With these and other objects in view the in-' vention may consist of certain novel features of construction and operation as will be morefully described and particularly pointed out in the specification, drawings and claims appended hereto.

In the drawings which illustrate an embodi ment of the invention and wherein like" reference characters are used to designate like parts- Figure 1 is an elevational view of an expansion tank embodying theimproved counter-balancing means of the invention whereby the roof may be caused to operate at relatively low pressures;

Figure 2 is a fragmentary vertical sectional view illustrating the arrangement of double sheaves, cable and counterweight comprising the invention for counter-balancing an expansion roof; and

Figure 3 is an elevational view of the counter balancing means shown in Figure 2' illustrating the manner of attaching the sheaves and cable tothe tank and roof.

Referring to the drawings, the invention i illustrated as applied to an expansion roof tank having acylindri'cal wall H a. bottom H which: may rest directly on the earth orother suitable support, and amovable roof designated in its entirety by numeral 12. Thecylindrica} wall I I] and bottom H provide an open" top tank which is closed by the movable roof to retain gases or liqids withinthe structure; The movable roof is of the bell holder type andaccordingly the cylindrical wall Ill of the tank is provided with a launder l3 including" a base or bottom member formed by the angle l4 suitably secured as by welding to the cylindrical wall of the tank. The launder is located exteriorly of the tank adjacent the upper portion thereof and the Vertical wall I 5 of the launder is reinforced by the angle memher to suitably secured as by welding to the top edge of th'e'wall l5 and located exteriorly of the same; Thetop edge of th cylindrical wall Ill is likewisereinforcedby the angle member I! having location within the'tank. and extending circ'umferentially thereof The movable roof essentially consists of a center portion i8 covering the entire area'of the open top tankstructure. i Said center portion l8 may have thegeneral shape of a flattened cone, as best shown in Figure 1'. welded to the circumference of thecenter portion 18, the sameextending substantially horizontally,

skirt or dip ring 22 havin location within the launder It. The dip ring functions to seal the interior of the. tank since the launder contains liquid and at the same time permits vertical movement of the roof to take place. Y

A depending rain shed skirt- 23-is suitably supported from the outer edge of the peripheral portion 28. The rain shed skirt has a length almost equal to that of the launder I3 and for thepurposes of theinvention the said rain shed skirt is suitably reinforced at intervals by the vertically extending structural members 24, as shown. in Figure 3; The upper corner angle 25 functions as asecuring element for joining the rain shed A peripheral portion 20 is skirt to the roof and the angle 26 fixed to the lower edge of said skirt 23 and extending outwardly of the same strengthens the lower edge. At intervals around the circumference of the rain shed skirt at those places where a counterweight structure is to be located, said rain shed skirt is provided with a depending bracket member 21, the same depending from and being suitably secured to angle 26.

Upward movement of the expansion roof 12 will increase the vapor space within the tank, which action is necessary to retain the volatile vapors produced during the heat of the day. The dotted line position of the roof shown in Figure 1 represents the fully expanded position of the same. As a result of the cooler night temperatures the vapors are condensed and the roof accordingly returns to initialposition. The volatile fractions of the liquid stored in the tank will thus be conserved and substantially the same procedure takes place upon filling of expansion roof storage tanks since the filling operation increases the production of vapors which are accommodated by upward movement of the roof.

Unless counter-balancing means are employed the'vapor pressure necessary to cause upward movement of the expansion roof I2 is determined primarily by th weight of the roof including the weight-of any stabilizing means having fixed relation therewith and which move with the roof. However, by counter-balancing the dead weightofsuch 'a roof it is possible to secure operation at much lower pressures. In actual practice it is desirable that tanks equipped with expansion roofs'operate on less than one ounce per square inch pressure. If such operation an be secured the expansion tank can be used to store the vapors --from a number of conventional fixed'roof tanks.- i 1 Th counter-balancing means of the invention comprises counterweights which act on the roof through the depending rain shed skirt. Thus the counterweights are located exteriorly of the tank. An arrangement of doubl sheaves is employed, with the result that the counterweights are reduced in weight by half but are required to travel twice the distance travelled by the movable roof for each movement thereof.

' The upper sheave 3ll is suitably supported by means of the hanger 3| which is pivoted at 32 to the bracket 33. The bracket 33 is part of the reinforcing means for the launder since said bracket is suitably secured to angle I6 as by welding and is likewise welded along its inside edge tow'all I of the launder. The lower sheave 34 is likewise supported by hanger 35 pivoted at 36 to bracket 3 projecting inwardly from the lower edge of the depending bracket member 21. It will be observed that whereas sheave 30 depends downwardly, the sheave 34 extends upwardly. The cable 38 therefore passes over sheave 30 and under s'heave3'4. One end of th cable is fixed to the tank, more particularly at the upper edge of the launder, by means of a suitable connection. Said connection may take the form of a'bracket 40 secured to the angle [6 and a clevis 4| for joining the end of the cable to said bracket in a pivotal manner. The opposite end of the cable is suitably fixed to the counterweight 4:2 by means of the eye bolt 43.

During operation of the counter-balancing apparatus of the invention th counterweights 42 will move vertically and since said weights are suspended from sheaves 30 relatively close to the cylindrical wall H] of the tank, roller means are provided to maintain each weight in proper spaced relation and facilitat movement of the same. As clearly shown in Figures 2 and 3, each counterweight 42 carries a pair of rollers 44 disposed on the respective sides of the same. Any suitable form of journalling and supporting means, such as the brackets 45, may be employed, projecting from the respective sides of the counterweight. The double arrangement of sheaves makes it possible to reduce the weight of the counterweights 42 by approximately one-half that which would otherwis be required for enabling the expansion roof to operate at a predetermined pressure. The sheave 34 and counterweight 42 constitute the movable elements of each arrangement. When th roof moves in an upward direction for expansion purposes, for example, each sheave 34 will also move in an upward direction, with the result that the counterweights will travel downwardly and the degree of movement of each counterweight will be twice the travel of sheave 34. With the reduction in the weight of the counter-balancing means a reduction is also secured in the size of the sheaves and cable.

What is claimed is:

1. In a tank having an expansion roof with sealing means between the roof and the tank shell, a rain shed skirt depending from the'periphery of the roof and encircling the tank shell adjacent the upper portion of the tank, a plurality of upper sheaves supported in spaced relation around the upper edge of the tank shell,

lower sheave secured to the lower edge of therain shed skirt in spaced relation corresponding to that of the first mentioned sheaves, whereby certain upper and lower sheaves arevertically aligned to form airs, cables anchored at one 2. In a tank having an expansion roof with.

sealing means between the roof and the tank shell, a rain shed skirt depending from the .periphery of the roof and encircling the tank shell adjacent the upper portion of the tank, and counter-balancing means for said roof including weights, cable means for supporting each weight from the upper edge of the tank shell, and sheaves secured in spaced relation around the upper edge of the tank shell and the lower edge of the rain shed skirt respectively, each said cable means passing under a sheave secured to the skirt and passing over a sheave secured to the tank shell, whereby said weights have movement in a vertical direction which is twice the distance travelled by the expansion roof.

3. In a storage container for gas or liquid, an

open top tank arranged to provide a body of'seal ing liquid, an expansion roof movable with respect thereto to vary the vapor space within the tank, said roof having a depending peripheral skirt located within the sealing liquid, so as to confine the gaseous medium within the tank, a rain shed skirt depending from the periphery of the roof and encircling the tank adjacent the upper portion, a plurality of upper sheaves supported in spaced relation around the upper edge of the tank, brackets depending from the lower edge of the rain shed skirt in spaced relation substantially corresponding to that of said sheaves, a lower sheave secured to each bracket, cables anchored at one end to the upper edge of the tank, and each extending downwardly to pass under a lower sheave and then upwardly to pass over an upper sheave and depend therefrom, and a counterweight secured to said opposite depending end of each cable.

4. In a storage container for gas or liquid, an open top tank arranged to provide a body of sealing liquid, an expansion roof movable with respect thereto to vary the vapor space within the tank, said roof having a depending peripheral skirt located within the sealing liquid so as to confine the gaseous medium within the tank, a rain shed skirt depending from the periphery of the roof and encircling the tank adjacent the upper portion, and counter-balancing means for the roof including a plurality of weights located in spaced relation around the exterior of the tank, cable means for suspending each weight from the upper edge of the tank, and sheaves secured in spaced relation around the upper edge of the tank and around the lower edge of the rain shed skirt respectively, each said cable means passing undera sheave secured to the skirt and passing over a sheave secured to the tank, whereby said weights have movement in a'vertical direction which is twice the distance travelled by the expansion roof.

5. In a storage container for gas or liquid, an open top tank arranged to provide a body of sealing liquid, an expansion roof movable with respect thereto to vary the vapor space within the tank, said roof having a depending peripheral skirt located within the sealing liquid so as to confine the gaseous medium within the tank, a rain shed skirt depending from the periphery of the roof and encircling the tank adjacent the upper portion, and counter-balancing means for said roof including a plurality of weights located in spaced relation around the exterior of the tank, cable means for suspending each weight from the upper edge of the tank, and upper and lower sheaves arranged in pairs around the tank, the upper sheave of each pair being secured to the tank and the lower sheave being secured to a bracket depending from the rain shed skirt, and each said cable means intermediate its ends passing under the lower sheave of the pair associated therewith and over the upper sheave of said pair, whereby said weights have movement in a vertical direction which is twice the distance travelled by the expansion roof.

6. In a tank having an expansion roof with sealing means between the roof and the tank shell, a rain shed skirt depending from the periphery of the roof to form a weather hood, upper, sheaves pivotally suspended from the upper edge of the tank shell in spaced relation, lower sheaves pivotally secured to the lower edge of the rain shed skirt and correspondingly spaced so that the sheaves form substantially vertically aligned pairs, a cable for each pair, each cable having one end fixed to the tank shell and depending downwardly to pass under a lower sheave and upwardly to pass over an upper sheave and depend therefrom, and a counterweight secured to the depending end of each cable.

7. In a tank having a stationary shell member and a vertically movable roof member, pairs of superposed sheaves on said members, the sheaves on said shell member being located above the sheaves on said roof member, and elongated, flexible means extending over the upper sheave of-each pair and under the lower sheave of each pair, and having one end secured to said shell member, and a counterweight for said roof member secured to the other end of each of said elongated, fiexible means.

PHILIP S. GRAVER. 

